If you have a history of a heart attack or if you have what we call chronic angina, you most likely have been given a prescription for Nitroglycerin by your doctor. If you're at home and you experience chest pain, which you consider to be your typical angina, you should take your nitroglycerin. We say take two nitroglycerin or five minutes apart, but if you don't have any relief of your chest pain, you should call 911 ASAP. So what Nitroglycerin does is it causes vasodilation, allowing more blood flow to the areas of your heart that lacks oxygen as a result of the blockage.